Pyroelectric detector devices, such as the pyroelectric vidicon, are generally well known in the field of infrared imaging and have been constructed using a variety of known pyroelectric materials, such as lithium tantalate and lithium niobate, as the basic IR radiation-to-signal voltage conversion medium of the detector. The pyroelectric detector has been used in a wide variety of applications in the field of thermal imaging, and a recent discussion of the pyroelectric vidicon may be found, for example, in an article by A. G. Shepard entitled "Today's Infrared Reading Vidicons Map Clearer Pictures", Electronics, pp. 99-105, Nov. 24, 1977. Other diverse forms of pyroelectric detectors are disclosed respectively by Byer et al in U.S. Pat. No. 4,060,729, by Turnbull et al in U.S. Pat. No. 4,053,806, by Roundy in U.S. Pat. No. 4,072,863, by Sher in U.S. Pat. No. 4,058,729, by Roberts et al in U.S. Pat. No. 4,044,374, and by Conklin in U.S. Pat. No. 4,047,070, and all of the above-identified references are incorporated herein by reference.
In one type of pyroelectric detector construction particularly relevant as prior art to the present invention, a pyroelectric substrate material such as lithium tantalate has a continuous thin metal infrared absorbing layer deposited on one surface thereof to receive thermal radiation from an object or scene within a particular field of view (FOV). The reverse surface of the pyroelectric substrate includes a plurality of metallic readout electrodes which form a particular grid pattern from which an output signal voltage may be derived. This readout grid pattern may be coupled to chosen digital or analog readout circuitry, typically including serial voltage-controlled devices, such as charge-coupled devices (CCD's), whose output may in turn be applied through conventional signal processing circuitry to a video camera or the like. The size, shape and spacing of the readout grid pattern on the pyroelectric substrate will, of course, depend upon the particular application in which the detector is used. One example of this type of pyroelectric detector is disclosed in U.S. Pat. No. 4,032,783, of N. J. Koda, assigned to the present assignee.
In order to prevent unacceptable heat transfer and thermal loss from the pyroelectric material of the detector, which loss in turn causes a reduced detector responsivity, the readout grid electrodes or pattern on the reverse side of the pyroelectric substrate have traditionally been thermally insulated to some degree from their immediate support member or housing. This has been accomplished using various approaches to minimize heat transfer from the pyroelectric material to the support member. One of these prior approaches is to use insulating spacers between electrodes on the reverse surface of the pyroelectric material and an underlying support member, and these readout electrodes are connected to other external signal processing circuitry by means of wires or pins extending through the insulating spacers. Another prior approach is to use insulating pads which have been coated with a thin metal film as a means for connecting the pyroelectric material and the reverse-surface electrode members thereon to an underlying support and readout electrode member. But in both of of these direct (DC) substrate interconnect techniques, there will be some undesirable heat transfer and loss by thermal conduction from the pyroelectric material and through the metal interconnect to the underlying support and readout member.
In practice, this detector support member will frequently provide support and electrical readout for a large number of these pyroelectric detectors positioned in a chosen array, so that the particular thermal isolation techniques used to satisfactorally thermally insulate a large plurality of these pyroelectric substrates can become quite complicated. However, when using either simple or complicated and sophisticated thermal insulation techniques for this purpose, there will nevertheless always be some direct conductive heat losses from the pyroelectric material as a result of the uninterrupted heat transfer path from the pyroelectric susbstrate material and the surface electrode members thereon, and through the metallic interconnect wires or pads to the readout circuitry in or on the adjacent detector support structure. Additionally, an increase in the complexity and sophistication of these detector insulation techniques will normally incrase the complexity and expense of these detectors or detector arrays and degrade their reliability.